-LRB- CNN -RRB- -- Four more cases of a possibly fatal respiratory virus have been confirmed in Oman and Saudi Arabia , according to the World Health Organization .

Three people in Eastern Saudi Arabia contracted the Middle East Respiratory Syndrome -LRB- MERS-CoV -RRB- and one of the patients has died , the WHO said . They ranged from 49 to 83 years old and all three had underlying medical conditions . The WHO is investigating what exposure might have caused their infections .

The viral respiratory illness was first reported in Saudi Arabia in 2012 and since spread to at least four countries in or near the Arabian Peninsula , according the Centers for Disease Control and Prevention .

MERS unlikely to cause pandemic -- for now , experts say

The WHO says it has confirmed the first case of the virus in Oman , where a 68-year-old man from Al Dahkliya region became ill October 26 and was hospitalized two days later .

Since September of last year , the WHO has confirmed 149 cases of MERS-CoV and 63 people have died from the illness .

No cases have been identified in the United States , according to the CDC . It 's believed the virus has spread through close contact with ill people .

Symptoms of the disease include fever , cough , shortness of breath , diarrhea and -- in severe cases -- renal failure and acute respiratory distress syndrome with shock .

The WHO is asking member countries to carefully review any case of severe acute respiratory infections .

Opinion : Why MERS virus is so scary

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Four new cases of Middle East Respiratory Syndrome reported , with one person dead

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World Health Organization says first report of illness in Oman

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Investigation is ongoing on how the virus may have spread

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63 have died of virus which has been confirmed in 149 people in Middle East